I'm learning how to play the piano and after practicing for an hour to an hour and a half my middle to upper back starts to hurt pretty bad. I was wondering if anyone knew what can be done to prevent this. I'm using a pretty basic portable one person bench.
The body is like a Jenga tower. As long as everything is aligned properly it can stand effortlessly because gravity pulls its center of weight straight down. The tower rests upon itself. The second that there is an imbalance, the tower gives in to gravity and falls.
Sitting at the piano, you too must have a balanced center of gravity. For instance, if you sit with your head pulled forward, that will pull on the muscles on the back of your neck and back. If you have a slouch, that too creates muscular pulls.
Ask your teacher to check your bench height and distance from the keyboard to make sure your body can be balanced. If you sit too high you may slouch which will cause pain. If you sit too low you may raise your shoulders which can cause pain.
If you have a bench with a cushion or padding, ditch it. Find a hard wood bench or better yet, one of those Steinway Chairs which have a slight forward declivity. Then sit at it with just enough of your butt on the edge to keep you from falling off. You hammies should not be on the seat. The seat is to balance you, not sit on. Just your coccyx and little more. Make sure you are sitting straight as if there is a string attached to the top of your head and you are suspended there. You should be free to lean forward, left or right.
When you play, there are always adjustments to your shoulder and elbow and slight leanings forward, your teacher should be making these adjustments to your repertoire. These movements also prevent static loading if you have an imbalance.
Pain simply means there is an imbalance and, your body is straining your muscles in an attempt to compensate. You don't need exercise, more practice, more muscle or anything else hocus pocus. You need an adjustment to how you sit and nothing more. Your body already has built all the muscle it needs to maintain balance. If you can go for a walk for an hour and your body is balanced and you have no back pain, you need to maintain that same balance when you sit down. When you ride a bike your body makes all these impossible adjustments so that you can balance on a one inch wheel. When you sit down your body needs to do the same but often we use our butts to sit on and that tells the brain that we don't need to balance and the ancillary muscles rest instead of working. Then the larger muscles become taxed.
Your body works in opposites so if your back hurts it is a good guess that it is something in front of you that is causing the problem. Maybe your arms may be too far from the keyboard or your head is falling forward because you are looking down.
First, I suggest that you take frequent breaks, in which you do some dynamic stretches and arm movements to free things up. Also:
make sure your shoulders are not hunched up which you're playing
it's easy to get caught up in finding the right notes, and this can make practicing a very intellectual activity. Spend some time every day on repertoire -- a couple of pieces you know well already -- and play through them with a focus on the phrasing and expressiveness, to practice loosening up your body and letting it express your phrasing ideas.
As you do this, be aware of the different kinds of circles your body makes. For example: (1) your two feet allow energy to flow like a tuning fork. Energy flows out one foot, through the floor, and up your other foot. That's one circle. (2) When you play an isolated note with one hand, followed by a rest and another note, if you allow your arm to come up and then come down again for the next note, you have just traced a circle in the air with that hand! (3) Your torso can lean from one side to another with your phrasing. You can do this as a circle that involves side to side motion as well as up and down motion. (4) Your head can be a conductor, coming up with the final upbeat and coming down at the beginning of the next measure. That's a circle. (5) Learn to use your diaphragm when breathing. This is also a circle. (6) Lean to the left, then lean to the right -- in a way that makes sense with the phrasing. Combine this with leaning forward or back -- and voilà, you have another circle. These movements don't need to be large to be effective. (Etc. you may find some additional circles.)
The idea here is to try not to use your body in a purely static way. Imagine if you were asked to hold out a heavy book straight out in front of you without moving -- that would be very hard on your body -- torture, in fact! Also, try not to use just your arms, or just your fingers. Let the fine movements be led by gross motor movements.
Watch pianists in live concerts and video recordings, to open up your horizons to the many ways the body can lead the parade, so to speak.